This invention relates to certain 2,2,6,6-tetraalkyl-piperidine compound stabilizers for synthetic polymers and to an improved process for their preparation.
Many 2,2,6,6-tetraalkylpiperidine compound stabilizers are known. For a summary of the art, M. Minagawa et al. U.S. Pat. No. 4,124,564 of Nov. 7, 1978 can be consulted at column 1 line 15 to column 2 line 45. In particular, hindered piperidine alcohol compounds having Formula A, which can be named 2,2,6,6-tetramethyl-4-piperidone spiroketal carbinol compounds, or more systematically 9-aza-3-hydroxymethyl-3-alkyl-8,8,10,10,-tetramethyl-1,5-dioxaspiro(5,5) undecanes, ##STR5## have been disclosed by K. Murayama in U.S. Pat. No. 3,899,464 of Aug. 12, 1975 as stabilizers able to protect syntheticpolymers and plastics against the harmful effects of exposure to ultraviolet radiation and heat. Compounds of Formula A have also been disclosed to be valuable synthetic intermediates for the preparation of even better stabilizers by reaction of the compounds at the alcoholic hydroxyl group to form various derivatives. Outstandingly effective stabilizers among these derivatives are certain organic phosphite esters disclosed by M. Minagawa et al in U.S. Pat. No. 4,096,114 of June 20, 1978; hydroxyaliphatic dicarboxylic and tricarboxylic acid esters disclosed by M. Minagawa et al in U.S. Pat. No. No. 4,105,625 of Aug. 8, 1978; diol bis-carbonate esters disclosed by M. Minagawa et al in U.S. Pat. No. 4,115,476 of Sept. 19, 1978; butane-and butenetricarboxylic acid esters disclosed by M. Minagawa et al in U.S. Pat. No. 4,116,927 of September 1978; heterocyclic carboxylic acid esters disclosed by M. Minagawa et al in U.S. Pat. 4,118,369 of Oct. 3, 1978; and aliphatic tetracarboxylic acid esters disclosed by M. Minagawa et al in U.S. Pat. No. 4,136,081 of Jan. 23, 1979.
M. Minagawa et al. in U.S. Pat. No. 4,128,608 of Dec. 5, 1978 disclosed a class of 2,2,6,6-tetramethyl-4-piperidyl spiro aliphatic ether stabilizers having the general formula ##STR6## wherein R.sub.1 is selected from the group consisting of hydrogen, lower alkyl and lower hydroxyalkyl having one or two carbon atoms; ##STR7## R.sub.3 is selected from the group consisting of hydrogen and O; and n is 0 or 1.
Minagawa et al. disclosed preparation of these compounds by an acidcatalyzed condensation reaction in non-polar organic solvents such as benzene and toluene.